Fig. 3. Immunoperoxidase staining with QCPN antibody of chick-quail chimeras sacrificed at E19-E20. Quail nuclei (dark brown) are detected within and around the wall of intramuscular blood vessels (arrow in A) and also among and sometimes adjacent to developing muscle fibers. Quail nuclei are also seen inside cross-striated muscle fibers (B,C). (D,E) Double immunofluorescence staining with QCPN antibody reveals quail nuclei (red) in skeletal (D) and cardiac (E) muscle cells that express sarcomeric myosin (green). Quail nuclei appear red in the interstitium and orange when inside myosin-positive cells. Scale bar: 25 µm.